The present invention relates to a storage system and the control method thereof.
In recent years, data life cycle management (DLCM) is attracting attention as a method for managing a storage system. DLCM is a concept of realizing a more cost efficient data management method by managing data migration between storage systems according to the value of data that changes with time. For instance, since an email system is positioned as a mission-critical system of enterprises, it is necessary to use a high-end storage system having high performance and high reliability. Since the access frequency will decrease with emails that are few weeks old, data is migrated from the high-end storage system to a nearline storage system. Although a nearline storage system is inferior to a high-end storage system in terms of performance and reliability, there is a merit in that it is inexpensive, and instant access is possible as required. And, after the lapse of 1 to 2 years after the migration of data to the nearline storage system, such data is migrated to a tape medium and stored in a cabinet. In order to reduce the data management cost based on the concept of DLCM, the management of data migration is important.
Japanese Patent Laid-Open Publication No. 2005-157710 discloses, as technology for taking the concept of DLCM one step further, technology referred to as MAID (Massive Arrays of Inactive Disks) for reducing the power consumption by shutting off disk drives that are not accessed for a long period of time. Pursuant to the increase of storage capacity demanded in a disk array system, the number of disk drives to be mounted is of an exponentially increasing trend, and the power consumption of the disk array system can be effectively reduced by employing the MAID technology.